Bellator veteran Jessica Penne scored a significant upset this evening in her shoot boxing debut in Tokyo, Japan. Penne earned a Majority Decision win over promotional postergirl Rena Kubota after a pair of extension rounds in a razor-thin bout at Shoot Boxing: “Act.4″ at the famed Korakuen Hall.

After three back-and-forth rounds where both fighters landed solid strikes, Kubota looked to take control in the first extension round, but the bout was again ruled a Draw. In the fifth and final round, Penne earned a Shoot Point for a high-arc throw and that was just enough to win on two scorecards.

Penne (1-0-0 SB) landed a nice right cross in round one, but Kubota (16-5-1 SB/KB) was effective with a variety of kicks. Kubota continued to land kicks throughout the round, but Penne connected with two good counterpunches and neither fighter could secure a throw with enough arc to earn a Shoot Point. Kubota was effective with punches in the second round, but Penne countered with a headlock and tried for a throw. Kubota defended, but Penne managed to throw her for a much-needed Shoot Point.

Kubota was aggressive with strikes in round three and continued to land kicks, but struggled to find her range with punches as Penne sidestepped and avoided damage. Penne clinched and was much more effective in the grappling exchanges, where she looked to take Kubota down to the mat. Kubota tried for a guillotine choke midway through the round, but Penne defended and the close round came to an end. One judge scored the fight 30-29 for Penne, while the remaining two opted for 29-29 Draws.

In the first extension round, Kubota landed body kicks and jabs as Penne appeared to fatigue and slow down. Penne tried to clinch, but the Japanese star was able to stay out of reach and continued to score with kicks and counterpunches. Despite appearing to have won round four, Kubota was forced to fight on to a fifth round after the judges were divided in their verdict. Scores were 10-9 Kubota, 10-9 Penne and 10-10 for a Split Draw.

Penne took the momentum away from Kubota early in the fifth and final round after scoring a throw for a Shoot Point. Kubota secured a throw of her own, but it was not high enough to earn a point. She landed a nice kick to the face, however, but Penne remained the more effective fighter in the clinch and tried for takedowns throughout much of the second half of the round. The fight went to the scorecards again.

Winner: Jessica Penne by Majority Decision (10-9, 10-9, 9-9) after a second extension round and fifth round overall. She improves to 1-0-0 in shoot boxing.

With the big victory, Penne will likely be invited back to Shoot Boxing in the future. Another Bellator veteran who has had recent success in the unique sport, Toby Imada, dropped a Unanimous Decision in tonight’s Shoot Boxing main event. Kubota, whose younger sister Mio was victorious earlier in the night, is scheduled to rematch Erika Kamimura in a November title fight for the RISE promotion. It remains to be seen whether her shocking upset loss tonight will impact that bout.